The present invention relates to an earth leakage breaker with overcurrent protection and ground fault protection functions in a low voltage distribution system. In particular, the invention relates to a structure for posterior mounting type earth leakage operation output switch, as an internal accessory device of an earth leakage breaker that electrically indicates an earth leakage trip operation of the earth leakage breaker.
Known protection devices in a low voltage distribution system include a molded case circuit breaker and an earth leakage breaker. An earth leakage breaker produced in these days in Japan generally has an integrated structure assembling the parts for overcurrent protection function and the parts for ground fault protection function together in a single main body housing that has the same external dimensions as those of the molded case circuit breaker.
Circuit breakers such as molded case circuit breakers and earth leakage breakers have various internal accessory devices including an auxiliary switch for electrical indication of ON, OFF states of a breaker, an alarm switch for indicating trip state, a voltage trip device and the like as optional devices in order to flexibly deal with a system change in the user side. The internal accessory devices can be installed to be taken out afterwards in a recess formed in a cover of a main body housing (for example, Patent Document 1).
Conventional earth leakage breakers are normally equipped with an earth leakage indicating button of a pop-up type as a means for indicating the earth leakage trip operation (the indicator button projects from the cover of the main body housing in the earth leakage trip operation). Different from this means, an earth leakage operation output switch (a micro switch) for electrically indicating the earth leakage trip operation is installed in a known earth leakage trip device (for example, Patent Document 2). FIGS. 16(a) and 16(b) show an assembly structure of the prior art.
Referring to FIGS. 16(a) and 16(b), the reference numeral 1 designates an earth leakage trip device mounted on a main body housing of the breaker. The earth leakage trip device has a structure wherein the essential components including a trip coil 3 (a plunger type electromagnet in combination of a retaining magnet and a driving spring), an earth leakage indicating button 4, and an earth leakage operation output switch 5 responding to earth leakage trip operation are permanently installed in a unit case 2 (a molded resin casing).
The earth leakage operation output switch 5 employs a micro switch with its actuator lever 5a arranged opposing a movable iron core 3a of the trip coil 3 in the unit case 2. The movable iron core 3a of the trip coil 3 is driven in the direction of the arrow on receiving an earth leakage detection signal from an earth leakage detection circuit. Corresponding to the movement of the movable iron core 3a, an actuating slider (not shown in the figures) strikes a trip crossbar of the breaker to trip a contact switching mechanism, and at the same time, the movable iron core 3a pushes an actuator lever 5a of the micro switch towards inside of the micro switch. As a result, a contact (a “make” contact) of the earth leakage operation output switch 5 turns ON to output an earth leakage operation signal. In FIGS. 16(a) and 16(b), the reference numeral 5b designates a plunger that transmits the movement of the actuator lever 5a to a movable contact of the micro switch.
Patent Document 1: Japanese Unexamined Patent Application Publication No. H6-236726 (U.S. Pat. No. 5,581,219)(FIG. 1-3)
Patent Document 2: Japanese Unexamined Patent Application Publication No. H9-63453 (FIGS. 1-3)
Earth leakage breakers mounting the earth leakage trip device having the conventional structure as described above have following problems from a viewpoint of a user side. In the conventional structure shown in FIGS. 16(a) and 16(b), the earth leakage operation output switch 5 is fixedly installed in the casing of the earth leakage trip device 1 and engaged with the movable ion core 3a of the trip coil 3, and the earth leakage breaker equipped with the earth leakage trip device 1 is shipped as a product incorporating the earth leakage operation output switch 5 at the time of shipment.
For the users without using electrical indication of the earth leakage operation in the system employing an earth leakage breaker, the earth leakage operation output switch permanently incorporated in the earth leakage breaker deserves an excess specification. On the contrary, the users that purchased an earth leakage breaker with standard specification that is not equipped with an earth leakage operation output switch, cannot add an earth leakage operation output switch to the earth leakage breaker as it is. Consequently, these users can make a system including electrical indication of the earth leakage operation only by asking the manufacturer to exchange the earth leakage trip device for the one equipped with an earth leakage operation output switch, or by newly purchasing another earth leakage breaker with an earth leakage operation output switch. This is hardly dealt with by the users.
In light of the above problems, it is an object of the present invention to provide an earth leakage breaker capable of indicating earth leakage operation by an electric signal, wherein a user can install later an earth leakage operation output switch as an optional internal accessory device similar to an auxiliary switch and an alarm switch, onto an earth leakage breaker of standard specification. The invention also provides a structure for mounting an earth leakage operation output switch afterwards.
Further objects and advantages of the invention will be apparent from the following description of the invention.